Retaining device for an instrument

ABSTRACT

The invention relates to a retaining device for an instrument, comprising at least one joint having at least two parts that can be moved relative to each other and at least one drive unit associated with the joint. The drive unit is designed to move the joint by driving at least one of the parts of the joint that can be moved relative to each other. The retaining device also comprises a securing device, which has a locking mechanism associated with the joint and a release unit that can be activated, wherein the locking mechanism interacts with the release unit in such a way that the locking mechanism holds the joint in a locked position as long as the release unit is not activated. The securing device is designed to permit a motion of the joint out of the particular locked position within a specified range of motion even if the release unit is not activated. The invention further relates to a corresponding securing device for a retaining device and to an operating method for said securing device.

The present application is a divisional of and claims the benefit toU.S. patent application Ser. No. 13/810,230, filed on Apr. 23, 2013,which is a national stage entry of PCT/EP2011/003519, filed on Jul. 14,2011, which claims priority to German Patent Application No.102010027248.5, filed on Jul. 15, 2010, the contents of which are hereinincorporated by reference in their entirety.

The present invention relates to a retaining device for an instrument,said device exhibiting at least one joint, with at least two parts thatare movable relative to one another, and at least one drive unitassigned to the joint. The drive unit is designed to move the joint bydriving at least one of the parts of the joint that are movable relativeto one another.

Driven retaining devices of such a type are already known from the stateof the art. Depending upon the type of application, such a retainingdevice may be a so-called stand device, which retains a medical opticalinstrument, or a robot with a manipulation unit by way of instrument. Asa rule, the joint takes the form of a swivel joint, in which case a loadtorque is generated in the swivel joint by means of the parts of thejoint that are movable relative to one another and by means of theinstrument. The drive unit may introduce into the swivel joint acorresponding counter-torque which is suitable to compensate the loadtorque.

A retaining device of such a type is known, for example, from documentDE 10 2004 063 606 A1, wherein the retaining device includes an electricmotor for balancing the load torque, which has been combined with meansfor registering the position of the swivel joint and can be suppliedwith current in a manner depending on a registered rotary joint positionfor the purpose of generating a counter-moment balancing the loadtorque. For this purpose a control unit is provided which sets therequisite motor current.

So-called stand devices or retaining devices for retaining a medicaloptical instrument are ordinarily employed in order to enable a handlingof the instrument that is as easy as possible for the operating surgeonor for further medical staff. Accordingly, by means of the retainingdevice the medical optical instrument fitted thereto can be brought byhand into a desired position without the weight of the instrument havingto be held during the positioning procedure, and the retaining deviceholds the instrument in the desired position after completion of thepositioning procedure.

Ordinarily, the retaining device exhibits a securing mechanism whichensures that the instrument and the retaining device can be movedrelatively easily during the positioning procedure and which blocks amovement of the retaining device after completion of the positioningprocedure. For this purpose, as specified in document DE 10 2004 063 606A1, a magnetic brake may be provided in the swivel joint, which,depending on the activation, releases or prohibits a movement of theparts of the swivel joint that are movable relative to one another. Ifan operator would like to move the retaining device together with theinstrument, he/she firstly disengages the magnetic brake, by, forexample, pressing a release button, and then moves the instrument byhand into the desired position. As soon as he/she lets go of the releasebutton, the magnetic brake automatically engages again and blocks afurther movement of the parts of the swivel joint that are movablerelative to one another, so that the retaining device now retains theinstrument in the position that has been attained at this time.

While the operator carries out the positioning procedure and keeps thebutton for releasing the magnetic brake pressed, the electric motor, orgenerally a drive unit, acts on the movable parts of the swivel joint insuch a manner that a load torque introduced into the swivel joint isbalanced by a counter-torque, so that the instrument can be displaced ina manner that is virtually weightless for the operator.

By virtue of such a securing mechanism it is made possible that a humanoperator, such as an operating surgeon for example, and a drivenretaining device can be deployed jointly without the retaining deviceconstituting a safety risk for the people located in the working spaceof the retaining device. The automatic engaging of the brakes as soon asthe operator is no longer actuating the securing mechanism prevents theretaining device from moving undesirably into a position in which it mayinjure a person. The braking action of the brakes is chosen in this casein such a way that the driving force of the drive unit is not sufficientto move relative to one another the parts of a joint at which the brakehas been engaged.

One problem that has become known in connection with retaining devices,and also generally in connection with robotic units of all types,consists in the vibration damping of the arrangement. In principle, bothunwanted post-oscillations after completion of the procedure forpositioning the retaining device and also external building vibrationswhich, depending on the type of mounting of the retaining device, can betransmitted to the retaining device via the ceiling of the room, sidewalls of the room or the floor of the room can be introduced into saiddevice and into the instrument connected thereto. Moreover, unwantedvibrations are also introduced into the retaining device and into theinstrument by an operator who knocks the retaining device, for exampleif he/she would like to use the instrument fitted to the retainingdevice (e.g. would like to look through a microscope). In order toeliminate such unwanted and disturbing vibrations of the instrument onthe retaining device as far as possible, from the state of the art it isknown to take additional vibration-damping measures.

A first known measure consists in decoupling, in vibration-dampingmanner, the retaining device from the room in which it is arranged, forexample by means of damping intermediate elements which may be arrangedbetween the wall to which the retaining device has been fitted and theretaining device itself. Intermediate elements of such a type can bevery elaborate and costly, particularly if they are to be suitable todamp vibrations of highly diverse frequencies. In addition, onlybuilding vibrations can be damped in this way, but not thepost-oscillations, discussed above, of the retaining device.

As a further measure, from the state of the art it is known to employsystems for active vibration damping in combination with the retainingdevice. Accordingly, published German patent application DE 10 2004 063606 A1 discloses a mechanism for active vibration damping, whichexhibits a sensor for registering vibrations of the retaining device,which provides a controlled variable for a vibration-damping controlloop. This vibration-damping control loop outputs, by way of correctingvariable, a superposed motor current to the electric motor, in orderthereby to move the swivel joint in such a way that a registeredoscillation or vibration of the retaining device is counteracted. Adisadvantage of such a configuration, however, is that oscillations orvibrations can only be compensated with this type of vibration dampingso long as the brake for securing the position of the retaining devicedoes not block the swivel joint.

However, it may be desirable or necessary to damp vibrations of theretaining device, and consequently also of the instrument, preciselywhen the retaining device is located in its retaining position (i.e.when the brakes are blocking the at least one swivel joint of theretaining device).

Therefore it is known, moreover, from the state of the art to enable thevibration damping via additional actuators or drive devices which aredifferent from the drive unit for moving the swivel joint. For instance,from document DE 10 2004 004 602 A1 it is known to provide a standdevice for a medical optical instrument with an additional drive, inorder to enable a vibration damping, whereby the drive may be connected,for example, to a control circuit or control loop.

Document DE 10 2007 034 286 A1 discloses an active vibration-dampingdevice for a stand, which comprises at least one vibration pick-up forpicking up a vibration to be damped and at least one additional actuatorfor generating a damping counter-vibration, wherein the separateactuator may include, for example, piezoelectric elements.

A similar arrangement is also known from document EP 1 447 700 A2, inwhich an ARES (actively reacting flexible structure) component isemployed by way of self-regulating component which, on the basis of themeasurement of vibrations, drives integrated drive elements, for examplepiezoelectric actuators, in such a way that they counteract thevibration in real time, so that the vibrations do not lead to a changeof position of the retaining device.

The provision of additional drive elements or damping elements of such atype, however, signifies in each case the necessity to have to integrateadditional elements structurally into the configuration of the retainingdevice. These elements entail an increased effort and hence increasedcosts not only within the scope of the design process but also duringmanufacture and assembly. Moreover, an increased inspection effortand/or repair effort may be associated with this, since these additionalelements have to be checked regularly as regards their functionality or,in the case of a defect, have to be exchanged or repaired.

Consequently an object of the present invention consists in enabling acost-effective and reliable vibration damping of the retaining devicewithout a safeguarding, provided by a securing mechanism, of the peoplelocated in the working space of the retaining device having to bedispensed with.

This object is achieved by means of a retaining device for an instrumenthaving the aforementioned features, which further exhibits a securingmechanism with a lock assigned to the joint and with a release unit thatis capable of being activated, wherein the lock interacts with therelease unit in such a manner that it holds the joint in a lockingposition so long as the release unit has not been activated, wherein thesecuring mechanism is set up to permit a movement of the joint within apredetermined range of movement out of the respective locking positionif the release unit has not been activated.

The securing mechanism of the retaining device according to theinvention consequently offers the desired safety which is generallyrequired in the case of an interaction between human and robot, by therobot or the retaining device being able to move completely freely onlywhen the release unit has been activated, that is to say, for example,by a user or operator keeping a release button pressed. If the releaseunit is deactivated again, then by reason of the specially designedsecuring mechanism the movement of the joint that is brought about bythe drive unit, that is to say, the driven movement of the joint, ispossible only within a predetermined range of movement out of therespective locking position, that is to say, out of the position inwhich the joint was located when the release unit was deactivated.

In this way, for example, a vibration damping can be effected with theaid of the drive unit assigned to the joint also when the retainingdevice has been locked, since a minimal movement of the joint within thepredetermined range of movement suffices for this. At the same time,however, the predetermined range of movement also ensures that theretaining device in the locked state cannot carry out any uncontrolledmovement that could endanger the safety of the people located in theworking space of the retaining device.

The term ‘instrument’ here encompasses both optical and/or medicalinstruments and suchlike as well as a manipulation unit of a robot.Moreover, the use of a retaining device according to the invention may,of course, also be sensible even when no instrument has been fitted tothe retaining device.

The lock further includes any non-positive, force-fitting and/orpositive, form-fitting type of connection that is able to connect to oneanother the parts of the joint that are movable relative to one anotheror is able to connect the drive unit to a part of the joint that is notdriven by the drive unit. Further configurations in which the lockconnects, for example, the drive unit in non-positive manner orpositively to another immovable part of the retaining device, in orderto block the latter, are also conceivable.

The joint may take the form of a swivel joint wherein at least one ofthe parts that are movable relative to one another can be swivelledabout an axis of rotation of the swivel joint. Alternatively, however,the joint may also take the form of a sliding joint that enables alinear motion of at least one of the parts that are movable relative toone another. In principle, a design is also conceivable in the form of ajoint that permits both a linear motion and a rotational motion of oneof the parts of the joint that are movable relative to one another, forexample in the form of a screw joint. In practice, however, use haspreferably been made hitherto of swivel joints or sliding joints, whereappropriate combined with one another.

The release unit may include a handle, a push-button, or any other typeof input unit that permits the intention of a user to move the retainingdevice to be discerned.

The drive unit of the present invention serves for moving the joint bydriving at least one of the parts of the joint that are movable relativeto one another. Therefore the drive unit—as known from the state of theart—can be utilized to compensate a load torque acting on the jointtaking the form of a swivel joint by introducing a counter-torque.Alternatively—that is to say, in the case of a mechanical full orpartial compensation of a load torque of such a type, wherein thecompensation is effected by virtue of the structural configuration ofthe retaining device—or in addition, the drive unit may, however, alsobe utilized for the purpose of vibration damping.

Accordingly, the retaining device may further exhibit a mechanism foractive vibration damping, which is configured to output to the driveunit a balancing signal which has the effect that the drive unit movesthe joint in such a manner that vibrations of the retaining device canbe balanced out. In this case, both torsional vibrations in a jointtaking the form of a swivel joint and vibrations in a joint taking theform of a sliding joint can be balanced out.

The drive unit can be controlled in known manner by a control unit whichoutputs a control signal to the drive unit for the purpose of balancinga load torque which is evoked by the instrument itself and/or by themovable parts of the swivel joint in the joint taking the form of aswivel joint. Said signal has the effect that the drive unit generatesin the swivel joint a counter-moment balancing out the load torque(active compensation).

Likewise, in the case of a design of the joint in the form of a slidingjoint, the drive unit, controlled by the control unit, can generate acounter-force for balancing a tensile force or compressive force in thejoint which is evoked by the force of the dead weight of the joint partsthat are movable relative to one another, and of elements, connectedthereto, of the retaining device.

If the drive unit is already being actively utilized for the purpose ofgenerating such a counter-moment or such a counter-force, for thepurpose of active vibration damping the mechanism outputs to the driveunit a balancing signal which is superimposed on the control signal andin this way brings about the vibration damping.

The same vibration-damping effect can, however, be achieved in the caseof a retaining device that does not display active compensation with theaid of the drive unit but rather displays a mechanical full or partialcompensation. In the case of a mechanical compensation of a load torque,the retaining device is constructed, for example, in such a manner thatthe retaining device is held in a state of equilibrium in every possibleposition by means of balancing weights. The compensation is effected inthis case by means of the balancing weights and by means of thebalancing effect of the force of the dead weight of the movable parts ofthe joint. In the case of a mechanical full or partial compensation, thedrive unit may consequently be utilized exclusively or at least partlyfor the purpose of generating the counter-vibration balancing out avibration.

Both the control unit and the mechanism for active vibration damping maybe provided with an internal or external sensor system—for example,sensors for registering the current joint position, for registering theapplied load torque or an applied tensile force or compressive force, orfor registering vibrations of the retaining device—providing measurementsignals which form the basis for the respective control signal orbalancing signal.

Moreover, the control unit can be controlled via an external inputinterface by an operator who, for example, specifies a certain positionof the joint. In this way, the drive unit not only serves for vibrationdamping and, where appropriate, active compensation but can also changethe position of the joint, enabling a remote-controlled operation of theretaining device.

The mechanism for active vibration damping may additionally also exhibitan input interface, via which certain inputs can be made by an operator.For instance, the vibration damping can be activated and deactivated orcan be limited to a certain vibration range.

The lock may further include at least one stop surface and at least onecounter-stop surface, which interact in order to hold the joint in itslocking position. In order to enable a lock in two mutually opposeddirections of motion of the joint, however, several mutually facing stopsurfaces and counter-stop surfaces may be provided.

The stop surface and the at least one counter-stop surface may bearranged on the most diverse parts of the retaining device, for examplein each instance on the parts of the joint that are movable relative toone another, on the movable joint part and on an immovable part of theretaining device, on the drive unit and on an immovable part of theretaining device, etc. It only has to be ensured that by this means thejoint can be held in a locking position if the release unit has not beenactivated.

In addition, the lock may include a brake, in particular anelectromagnetic brake, whereby a movable part of the brake is coupledwith the at least one driven part of the joint and whereby the at leastone stop surface of the lock is arranged on the movable part of thebrake and the at least one counter-stop surface is arranged on the atleast one driven part of the joint. Instead of being coupled with the atleast one driven part of the joint, the movable part of the brake may,of course, also be coupled with a drive output of the drive unit, whichis connected to the driven part of the joint.

Such a brake makes it possible to block the at least one driven jointpart, so that with the aid of the brake the joint is held in therespective locking position that it occupied when the brake wasactivated. The non-positive design variant of a brake in which themovable part of the brake comes into non-positive, force-fittingabutment with a further immovable part of the brake, which is coupledwith the retaining device or with an immovable part of the joint, hasthe advantage, moreover, that, given an appropriate design of theeffective braking force, the joint can still be moved, whereappropriate, by hand (by overcoming the maximal braking force or amaximal braking moment resulting therefrom), in order to be able to movethe retaining device into a desired position in the case of engagedbrakes and in the case of a failure of the retaining device.

Moreover, in particular the configuration of a brake in the form of aclosed-circuit brake, for example in the form of an electromagneticclosed-circuit brake, is an advantage, since by reason of its structuralconfiguration said brake exerts a braking force so long as no electricalvoltage is applied to it. In this way, it can be ensured that in thecase of a possible failure of the power supply of the retaining devicethe lock can hold said device automatically in a safety position inwhich an endangerment by virtue of a further, undesired movement of theretaining device is ruled out.

Alternatively or additionally, the lock may exhibit a stop, inparticular a stop pin, on which the at least one stop surface is formedand which can engage with a recess having at least two counter-stopsurfaces for locking the movement of the joint in two directions ofmotion. This configuration corresponds to a positive coupling of themovable parts of the joint or of the drive unit with a non-driven partof the joint. In one configuration in the form of a stop pin, the partof the lateral surface of the pin that comes into blocking contact withone of the counter-stop surfaces upon a movement of the joint forms thestop surface.

Such a stop may furthermore be capable of moving back and forth betweena first position, in which it locks the movement of the joint, and asecond position, in which it permits the movement of the joint.Accordingly, the counter-stop surfaces may be provided as firmly formedsurfaces which interact with a retractable and extensible stop or stoppin. The stop pin or stop may furthermore be biased in one of the twopositions, for example in the release position, so that upon anactivation of the release unit the stop is held in the release position,and upon a deactivation the stop is disengaged and by reason of the biasis automatically moved into the locking position. Possibleconfigurations for such a mechanism include, for example, a spring forbiasing the stop in one of the two positions, and a magnet or suchlikefor moving and holding the stop into and in the respective otherposition.

Furthermore, there may be provision that a clearance is provided betweenthe stop surface of the lock and the counter-stop surface in thedirection of motion of the joint. The clearance that is provided servesin this case to define the predetermined range of movement within whichthe joint can move if the release unit has not been activated, that isto say, the retaining device has been locked.

Moreover, there may be provision that at least one elastic intermediateelement is provided between the stop surface of the lock and thecounter-stop surface in the direction of motion of the joint. Thisconfiguration variant can be provided as an alternative to theaforementioned clearance or as an additional measure. In an alternativeconfiguration, the elastic intermediate element replaces the clearanceand, by reason of its elasticity, enables a certain movement of thejoint within a predetermined range of movement, even when the releaseunit has not been activated. The range of movement of the joint resultsin this case by virtue of the elasticity, that is to say, the resilienceof the elastic intermediate element, and by virtue of the force or thetorque, respectively, acting on the intermediate element and introducedby the drive unit.

By way of such an elastic intermediate element, a rubber element, arubber coating or suchlike may, for example, be provided. Alternatively,however, configurations of the element formed from an elastic materialother than rubber are also conceivable, for example leaf springs orsuchlike made of metal. The elastic intermediate element may furthermorebe fitted to the stop surface, to the counter-stop surface, or to bothsurfaces.

By provision of an elastic intermediate element, in addition anautomatic centering or alignment of the stop surface in relation to thecounter-stop surface as a result of the elastic restoring force of theelastic intermediate element is made possible. In the case of adeactivated release unit, as a result of an acting driving force or anacting torque of the drive unit the stop surface can, moreover, be movedtowards the counter-stop surface within the predetermined range ofmovement. In the process the elastic intermediate element is compressed,and the spacing between the stop surface and the counter-stop surface isdiminished. If the driving action of the drive unit, that is to say, thetorque acting or the driving force acting, is dispensed with, or if itis reduced so that the elastic restoring force is greater than theremaining driving action, the stop surface is set back relative to thecounter-stop surface (alignment) by virtue of the elastic restoringforce. In the configuration variant with a stop arranged between twocounter-stop surfaces and with two clearance-free elastic intermediateelements between the stop and the counter-stop surfaces, this results ina centering of the stop between the counter-stop surfaces.

As a result of this alignment or centering, it can be ensured that aftera free movement of the joint (with release unit activated) the stopsurface is always arranged in such a manner with respect to thecounter-stop surface that with release unit deactivated the elasticintermediate element can be deformed again, and in this way a furthermovement of the joint remains possible.

In principle it is also conceivable, however, to configure one or moreelements of the retaining device in such a manner that it exhibits orthey exhibit an elasticity that suffices to permit a movement of thejoint within the predetermined range of movement, and thereby to enablea vibration damping. The range of movement of the joint results in thiscase by virtue of the resulting elasticity, that is to say, theresulting resilience of the system in the region of the lock, and theforce or the torque, respectively, acting on the stop and introduced bythe drive unit.

In order, in the configuration variant with a stop, to make it possiblethat the joint can be locked in any instantaneous position with the aidof the stop, it is advantageous to provide a plurality of recesses withwhich the stop can engage.

Furthermore, the retaining device may exhibit a monitoring appliancethat is suitable to monitor whether the joint is moving within thepredetermined range of movement, and to provide a feedback concerningthis to the securing mechanism. Such a monitoring appliance may, forexample, be connected to the securing mechanism via a communicationline, so that the feedback is relayed to the securing mechanism in theform of an input signal to the securing mechanism.

In addition, on the basis of the feedback of the monitoring appliancethe securing mechanism can permit an activation of the lock. In thisconfiguration the activation of the lock is effected virtually in twostages: in the first stage, by a deactivation of the release unit themonitoring appliance, which is to monitor whether the joint is beingmoved within the predetermined range of movement, is activated. So longas this is the case, the lock is not activated, even though the releaseunit has been deactivated. In the second stage, the monitoring applianceindicates that the movement of the joint has departed from thepredetermined range of movement, so the lock is now activated by thesecuring mechanism and blocks the joint. This ensures that the jointcannot execute any movement going beyond the range of movement that is,for example, useful for vibration damping.

The monitoring appliance may exhibit at least one sensor for monitoringthe movement of the joint. Such a sensor may, for example, include asensor or encoder of the drive unit, for example a visual positionsensor or suchlike. It is particularly favorable to use a sensor that isalready present in the internal or external sensor system of the controlunit or unit for active vibration damping of the retaining device andthat is utilized to ascertain a precise position of the swivel joint.

The present invention further relates to a securing mechanism for aretaining device having the features set out above, and also to aworking process for it.

The invention will be explained in the following in exemplary manner onthe basis of the accompanying schematic Figures. Shown are:

FIG. 1 a schematic side view of a retaining device according to theinvention,

FIG. 2 a schematic, partially sectioned side view of a swivel joint of aretaining device according to the invention according to FIG. 1,

FIGS. 3a-e schematic detailed views of the lock mechanism according toFIG. 2, wherein these views show different positions and embodiments ofthe lock mechanism in perspective representation,

FIGS. 4a and 4b schematic, partially sectioned side views of the lockmechanism according to detail A of FIG. 2,

FIG. 5 a schematic, partially sectioned side view of a brake of aretaining device according to the invention according to FIG. 1,

FIG. 6 a schematic detailed view of the coupling of the brake accordingto FIG. 5 with a part of the joint of the retaining device according tothe invention, and

FIG. 7 a flow chart that describes the procedures within a securingmechanism of the retaining device according to the invention.

In FIG. 1 an embodiment, represented in greatly simplified form, of aretaining device according to the invention is shown in side view. Theretaining device is denoted generally by reference symbol 10. The device10 includes an instrument 12, for example, as illustrated, a microscopeor suchlike, which is connected to the retaining device 10. In theembodiment represented in FIG. 1 the retaining device 10 is arranged onthe floor B of a room. Alternatively, however, the retaining device 10could also, of course, have been fitted to the side walls or to aceiling wall of a room.

The retaining device 10 which is represented is constructed in the formof a so-called stand which exhibits several rigid elements 16, 18, 20(hereinafter designated as ‘arms’) which are connected to one another bymeans of several swivel joints 14. Accordingly, arms 16 and 18 areconnected to one another so as to be movable relative to one another bymeans of swivel joint 14 ₁, and arms 20 and 18 by means of swivel joint14 ₂. At the free end of the retaining device 10 an instrumentreceptacle 22 is fitted, which in turn is connected to arm 20 via aswivel joint 14 ₃. Depending on the type and design of the retainingdevice 10, in this way the instrument 12 can be moved about several axeswhich may be arranged parallel or transversely to one another. As analternative to the retaining device 10 shown, the present invention alsoencompasses, of course, retaining devices that include one or moresliding joints instead of, or in addition to, a swivel joint. Arbitraryjoint combinations with variably many and variably designed joints arepossible in this connection.

The following remarks on the mode of operation and configuration ofswivel joint 14 ₁ apply likewise to swivel joints 14 ₂ and 14 ₃.

Assigned to the individual swivel joints 14 of the retaining device 10are drive units (not represented), for example in the form of anelectric motor or suchlike, which serve to drive at least one of themovable parts of the swivel joint 14 and in this way to move it relativeto the other part. Accordingly, as shown in FIG. 2, arm 18 is movedrelative to arm 16 by a drive shaft 18 a connected to arm 18, exhibitingat its free end an interface 18 b via which it can be connected to thedrive unit in such a manner that the drive shaft 18 a together with arm18, driven by the drive unit, can move about an axis of rotation D.

In the embodiment shown in FIG. 2 the drive shaft 18 a extends through athrough-bore of arm 16, in which connection the shaft 18 a may besupported in low-friction manner within the through-bore (notrepresented). The configuration of the swivel joint 14 represented inFIG. 2 is, however, only exemplary; accordingly, the linkage 18 b to adrive unit may also be configured at a different place and in acompletely different way, such as, for example, with a drive shaft ofthe drive unit engaging with arm 18, with a drive unit engaging on theouter contour of arm 18 and suchlike.

Ordinarily in the case of a retaining device, such as the retainingdevice 10 according to the invention, the drive or the drive unit isprovided at each swivel joint 14. Said drive unit may serve to balanceout a load torque that is generated in the respective swivel joint 14,caused by the dead weight of the instrument 12 fitted to the retainingdevice 10 and of the individual elements of the retaining device. Forinstance, at swivel joint 14 ₁ a load torque is generated that resultsfrom the weight forces of all the elements connected to arm 18(inclusive of the instrument 12), and from the associated lever arm.

In order to be able to guarantee a manual handling (manual positioning)of the instrument 12 that is as simple as possible, the drive units inthe respective swivel joints 14 serve to balance out the respective loadtorque by an equally large counter-moment, so that in the case of amanual movement of the instrument 12 in the working space of theretaining device 10 the latter can be moved by an operator in virtuallyweightless manner, and inertias are also compensated (activecompensation). In any case, the friction forces arising in the swiveljoints 14, which (with lock disengaged) are slight and depending on theconfiguration of the retaining device likewise can—as can also inertiasarising—be compensated by the drive unit (active compensation), have tobe overcome by the operator who would like to move the instrument 12freely. Alternatively, the retaining device according to the inventionmay, however, also display in each joint a mechanical full or partialcompensation of load torques arising.

As can likewise be discerned in FIG. 2, swivel joint 14 ₁ (just likeswivel joints 14 ₂ and 14 ₃) exhibits in addition a lock, for example inthe form of a stop pin 26, which serves to couple with one another theparts of swivel joint 14 ₁ that are movable relative to one another, inorder in this way to block a rotational motion of swivel joint 14 ₁.With the aid of the lock the retaining device 10 can retain the desiredposition after completion of the positioning. As an alternative to apositive coupling, shown in FIG. 2, of the parts 16, 18 of swivel joint14 ₁ which are movable relative to one another, a non-positive couplingis also conceivable, as explained below. In addition, it is equallypossible to arrange the lock between the drive unit and the part 16 ofswivel joint 14 ₁ which is not driven by a drive unit, or between thedriven part 18 of swivel joint 14 ₁ and an immovable part of theretaining device 10, in order to couple these elements with one another.

A release unit 24 arranged on the instrument 12 forms, together with thelock, a so-called securing mechanism which serves to protect peoplelocated in the working space of the retaining device 10 againstunintentional movements of the retaining device 10. Accordingly, theretaining device 10 can only be moved freely within its entire workingspace when the release unit 24 has been activated, whereby in itsactivated state it interacts with the lock in such a manner that thelatter releases the swivel joint 14. As soon as the release unit 24 isnot activated, such a free mobility of the retaining device 10 in itsworking space is no longer to be possible, for safety reasons.

The release unit 24 may include a handle, a push-button, a joystick orany other type of input unit which the user can actuate or activate inorder to express the fact that he/she would like to move the retainingdevice 10.

By reason of its structure, the retaining device 10 according to theinvention also offers, besides the manual mobility described above, thepossibility to be moved automatically by means of a controller. Inprinciple, a control unit, which is not represented, generates, forexample for the purpose of building up a counter-torque in therespective swivel joint 14, a control signal which has the effect thatthe drive unit drives as desired at least one of the parts of the swiveljoint 14 that are movable relative to one another, and in this way movesthe swivel joint 14. Once the release unit 24 has been activated, theretaining device 10 may, however, also be moved into a desired positionby means of the same control unit or an additional control unit, by thecontrol unit controlling the corresponding drives of the swivel joints14 (remote-controlled operation).

Moreover, the retaining device 10 is configured in such a manner thatvibrations arising, for example due to a post-oscillation of theretaining device 10 after a positioning movement has to taken place(manually or automatically) or due to room vibrations which aretransmitted to the retaining device 10, for example via the floor B, aredamped. This is obtained via a mechanism for active vibration damping(not represented), which uses the drive units of the driven swiveljoints 14 for the purpose of vibration damping. To this end, themechanism for active vibration damping emits to the respective driveunit a balancing signal (where appropriate, superimposed on the controlsignal) which has the effect that the drive unit moves the swivel joint14 in such a way that vibrations of the retaining device 10 arecompensated. Ordinarily, such a balancing signal is configured in such amanner that it brings about a periodic movement of the swivel joint 14(exciter vibration) corresponding to the active vibration, whereby byvirtue of a phase shift of the exciter vibration relative to the activevibration the active vibration and the exciter vibration cancel eachother out.

In order that such an active vibration damping is still possible evenwhen the retaining device is not freely movable in the working space butis to remain in a retaining position, the securing mechanism is set upto permit a movement of the swivel joint 14 out of the respectivelocking position within a predetermined angular range if the releaseunit 24 has not been activated.

In a first configuration variant, the securing mechanism, as shown inFIGS. 2 to 4 b, includes a lock with at least one stop pin 26 (in FIGS.4a and b , two stop pins 26 are shown), the outer circumferentialsurface of which forms a stop surface 26 a. As represented in FIGS. 4aand 4b , each stop pin 26 can be moved back and forth between a firstposition, in which it locks the movement of the swivel joint 14, and asecond position, in which it permits the movement of the swivel joint.Each stop pin 26 is received in its first position in a recess 28 (inFIGS. 4a and b , two recesses 28 are shown) which exhibits counter-stopsurfaces 28 a and 28 b. Each stop pin 26 may be arranged on the part 18of swivel joint 14 ₁ driven by the drive unit or on the non-driven part16 of swivel joint 14 ₁, in which case the recesses 28, which providethe counter-stop surfaces 28 a and 28 b, are arranged on the respectiveother part of swivel joint 14 ₁.

The mechanism that is shown for moving the stop pins 26 back and forthcomprises, according to FIGS. 4a and 4b , a magnet M and also a springF. The spring F is received in the interior of the stop pin 26 andbiases the latter in such a manner that it is located in the firstlocking position if the spring F is relaxed. This is also indicated bythe arrow F_(spring) in FIG. 4a . Of course, other possible arrangementsof the spring F are conceivable.

The magnet M (which is intended to represent schematically a source ofmagnetic attractive force of any type whatever) serves to relocate thestop pin 26 into the second position thereof (cf. FIG. 4b ), in which itpermits the movement of the swivel joint 14. For this purpose, amagnetic force, symbolised by the arrow F_(magnet) as shown in FIG. 4b ,acts on the stop pin 26, as a result of which the spring F is biased. Inthe case of the magnet M it is a question not of a permanent magnet butrather of a magnet that is capable of being electrically activated, forexample in the form of a coil or suchlike. If the magnet M does not havecurrent applied to it, no magnetic force F_(magnet) acts on the stop pin26, so that the latter is moved back again into its first position as aresult of the spring force F_(spring) of the biased spring F (cf. FIG.4a ).

The mechanism that is shown for moving the stop is purely exemplary andmay, for example, be replaced by reversal of action or by using otherelements for the introduction of force.

In FIGS. 3a to 3c a possible configuration of the receptacles 28 withthe counter-stop surfaces 28 a and 28 b is shown, in which a stop pin 26is received in different positions relative to the counter-stop surfaces28 a, 28 b. Accordingly, the recess 28 is configured, as clearlyperceptible, in such a manner that a clearance is provided between thestop surface 26 a of the stop pin 26 and the counter-stop surface 28 aor 28 b in the direction of motion of the swivel joint 14 (indicated bythe arrow R), so that a slight movement of swivel joint 14 ₁ within apredetermined angular range is possible even when the lock has beenactivated.

In order to be able to enable a lock of the swivel joint 14 in, as faras possible, any conceivable position, it is necessary to provide aplurality of recesses 28 with corresponding counter-stop surfaces 28 a,28 b and also at least two stop pins 26, which are arranged relative toone another and with respect to the counter-stop surfaces 28 a, 28 bwith angular offset (relative to the axis of rotation D) in such amanner that at least one of the stop pins 26 is always capable ofengaging with a recess 28, even if the other stop pin is blocked by acounter-stop surface 28 b (cf. FIG. 3d ).

Moreover, the configuration of the stop pin 26 in the form of a circularcylinder according to FIGS. 2 to 4 b and the configuration of the recessaccording to FIGS. 3a to e are purely exemplary. Accordingly, in analternative embodiment, for example with conical or sawtooth-shapedstops and corresponding recess surfaces, an unwanted blocking of themovement of the stop pin 26 out of the second position into its firstposition can be very largely avoided by means of a counter-stop surface28 b (as shown in FIG. 3d ).

In addition, instead of, or in combination with, the clearance,discussed above, in the direction R of motion of swivel joint 14 ₁ it ispossible to provide an elastic intermediate element E between the stopsurface of the stop and the counter-stop surface 28 a, 28 b (as shown inFIG. 3e ), which permits a further movement of swivel joint 14 ₁ evenwhen the stop is already bearing against the elastic intermediateelement E (cf. FIG. 3e ).

The elastic intermediate element E may be arranged either on thecounter-stop surface 28 a, 28 b or on the stop surface 26 a. Forexample, it is conceivable to provide the stop pin 26 or a stop ofwhatever type with an encasement consisting of an elastic material, forexample rubber.

An alternative, non-positive type of lock may include a brake 30 (cf.FIGS. 5 and 6) which couples with one another either the parts 16, 18 ofthe swivel joint 14 which are movable relative to one another or thedrive unit with an immovable part, for example the arm that is notdriven by the drive unit (in FIG. 2, arm 16). An example of such a brake30 is a so-called electromagnetic closed-circuit brake which exhibits abrake disc 32 held under preload, which presses against a correspondingbrake stop surface 34 and in this way establishes the force-fit. Forthis purpose a spring F with a thrust washer 36 presses the brake disc32 against the corresponding brake stop surface 34. Only when anelectrical voltage is applied to the closed-circuit brake is the thrustwasher 36 moved by magnetic forces (which are generated by acoil-carrier 38 supplied with current) away from the brake stop surface34 and contrary to a biasing force F_(spring) of the spring F, so thatan axial spacing arises between the brake stop surface 34 and the brakedisc 32 of the closed-circuit brake. In this position the force-fit isannulled and the previously braked parts can be moved freely relative toone another.

The advantage of such a closed-circuit brake consists, in particular, inthe fact that in the event of a possible power failure the brake isautomatically activated and in this way the retaining device can beprevented from moving in undesirable manner as a result of its deadweight. A further advantage of a non-positive configuration of thelock—such as, for example, in the form of a brake—consists in the factthat the parts that are movable relative to one another can still bemoved, if necessary by overcoming the friction forces of theclosed-circuit brake that has been engaged, even when the lock isactive, making it possible, in the event of a system failure, to movethe retaining device manually out of a position of potential danger.

In the case of the brake 30 shown in FIGS. 5 and 6 the brake disc 32 iscoupled with the driven part 18 of swivel joint 14 ₁, whereas the brakestop surface 34 may, for example, be rigidly connected to the furtherpart 16 of swivel joint 14 ₁ or to an immovable part of the retainingdevice 10. The coupling of the brake disc 32 with the driven part 18 iseffected via a splined-shaft-like gearing 38 a on the outer peripheralsurface of a drive shaft 18 a of the driven part 18 with a substantiallycorresponding gearing 40 a on the inner peripheral surface of a centralrecess 40 of the brake disc 32. Each tooth of gearing 38 a exhibits twolateral flanks 42 a, 42 b which form the stop surfaces of the lockaccording to the invention, whereby the substantially correspondingrecesses on gearing 40 a each exhibit two flanks 44 a, 44 b which formthe counter-stop surfaces of the lock according to the invention.Between each stop surface and each corresponding counter-stop surface aclearance and/or an elastic element E (in FIG. 6 only one is representedin exemplary manner) is provided in the direction of motion R of part18, as also explained above in connection with the stop pin 26 withreference to FIGS. 3a to 3c and 3e . The elastic element E serves inthis case for the self-centering of the brake disc 32 relative to thedrive shaft 18 a of the driven part 18, which is linked via theinterlocking gearings 38 a and 40 a.

Finally, in FIG. 7 a flow chart is shown which represents in exemplarymanner the mode of operation of the securing mechanism of a retainingdevice 10 according to the invention. In this embodiment, in addition toor as an alternative to the configuration of the lock shown in FIGS. 2to 6, a software-based control of the securing mechanism is provided.

In a step S100 a controller of the securing mechanism checks whether therelease unit 24 has been activated. For this purpose, use may be made,for example, of a conventional push-button switch or sensor of any type,which is arranged on a holding grip, integrated into a push-button orarranged on a different type of input unit and which permits theintention of a user to move the retaining device 10 to be discerned.Upon activation and/or deactivation of the release unit 24, for exampleby pressure on the corresponding push-button, this push-button switch orsensor emits a signal to the controller of the securing mechanism. Ifthe controller of the securing mechanism receives, in a step S101, thesignal that the release unit 24 has been activated, it outputs to thelock a disengage signal, by virtue of which the lock is disengaged (stepS102). A prerequisite for this is, of course, that the lock is capableof being controlled, in whatever manner, by the controller. Such acontrol is possible, for example, in the embodiment shown in FIGS. 4aand 4b , wherein for the purpose of disengaging the lock the magnet Mhas current applied to it, moving the stop pin 26 into its secondposition (disengaging position).

After this, in step S103 the retaining device is freely movable manuallyor automatically within the entire working space of the retaining device10. If the release unit 24 is deactivated after completion of thedesired movement of the retaining device 10, that is to say, if thesecuring mechanism receives, in a step S110, the signal that the releaseunit 24 has not been activated, then, in a step S120 it likewisetransmits the signal for disengaging the lock (as described above understep S102), but additionally activates, in a step S130, a monitoringappliance (not represented) which monitors the movement of the at leastone swivel joint 14 of the retaining device 10. The following remarksare made with reference to a swivel joint 14 but also apply, of course,given a corresponding configuration of the retaining device, to severalswivel joints, such as the swivel joints 14 ₁, 14 ₂, and 14 ₃ of theretaining device 10, or to one or more sliding joints.

The monitoring appliance according to the present invention may use, forexample, an internal or external sensor system, that is to say, forexample, angle sensors by way of internal sensors of the swivel joint 14(or displacement-measuring sensors for a sliding joint) or externalsensors of a navigation sensor system (not represented) etc., in orderto obtain a precise indication of the position in which the swivel joint14 is located (ACTUAL position) and by what angle (or displacement forthe sliding joint) the joint 14 has, where appropriate, moved out of therespective locking position (angle of motion or motion displacement).

For this purpose, the monitoring appliance can, for example, store thatposition of the joint 14 as locking position in which the joint 14 waslocated at the time at which the securing mechanism received the signalthat the release unit 24 has not been activated (step S110). Startingfrom this locking position, the monitoring appliance can then checkwhether the joint 14 is being moved out of this locking position withina predetermined range of movement. For this purpose, the monitoringappliance can, for example on the basis of the locking position and thepredetermined range of movement, calculate a SET position and cancompare the latter with the ACTUAL position or can compare the angle ofmotion (or motion displacement), ascertained on the basis of the ACTUALposition, with an angle (or displacement) characterizing the SETposition (step S140).

In this connection, the predetermined angle or displacement or the rangeof movement can be adjusted or altered by an operator, depending on theapplication, or may comprise a fixed safety value. If in the course of acomparison of the ACTUAL position of the joint, or of the angle ofmotion of the swivel joint 14 (or motion displacement of the slidingjoint) with respect to a SET position or the predetermined angle(displacement), the monitoring appliance comes to the conclusion thatthe joint 14 is being moved within the predetermined range of movement(step S150), it transmits a positive feedback to the securing mechanism(step S160).

A check is then again made as to whether the release unit 24 has beenactivated (step S100), and in the case of a release unit 24 that isstill deactivated the lock remains disengaged (step S120) and themonitoring appliance activated (step S130). If, however, the monitoringappliance recognizes in a step S140 that the movement of the joint 14threatens to depart from the predetermined range of movement (stepS141), it transmits a negative feedback to the securing mechanism (stepS142). The latter then causes, in a step S143, a blocking of the joint14 by outputting a corresponding signal to the lock. In addition, anerror handling (S144) is initiated, within the scope of which a check ismade as to why the joint 14 is moving beyond the predetermined range ofmovement (S144).

The mode of operation of the securing mechanism described in FIG. 7 can,of course, be combined with the mechanical configuration of the lockaccording to FIGS. 2 to 6, whereby, where appropriate, the clearancebetween the stop surface and the counter-stop surface of the lock ischosen in such a manner that a blocking arises only when thepredetermined range of movement for a movement of the joint has beenexceeded. In this case the structural configuration serves as anadditional safeguard in case the control of the securing mechanismshould fail.

The retaining device according to the invention enables, by virtue ofits configuration, in particular by virtue of the configuration of thesecuring mechanism, that, on the one hand, the securing mechanism of theretaining device can continue to ensure the protection of a personlocated within the working space of the retaining device, and that, onthe other hand, also in a retaining position of the retaining device anactive vibration damping can take place by utilizing the drive units,which are already present, of the joints.

We claim:
 1. A retaining device for an instrument, comprising: asecuring mechanism including: at least one joint, with at least twoparts which are movable relative to one another; at least one driveunit; and a lock assigned to the at least one joint and with a releaseunit adapted to be selectively activated, the lock being configured tohold the at least one joint in a locking position so long as the releaseunit has not been activated, the at least one joint being assigned tothe at least one drive unit, and the at least one drive unit beingconfigured to move the at least one joint by driving at least one of theparts of the at least one joint which are movable relative to oneanother, wherein: the securing mechanism is configured to permit amovement of the at least one joint out of the respective lockingposition within a predetermined range of movement even when the releaseunit has not been activated to enable vibration damping, in a case wherethe release unit has not been activated and the lock has beendisengaged, the securing mechanism limits the movement of the at leastone joint to the predetermined range of movement, and in a case wherethe movement of the at least one joint departs from the predeterminedrange of movement, the securing mechanism activates the lock.
 2. Theretaining device according to claim 1, further comprising: a mechanismfor active vibration damping configured to output to the at least onedrive unit a balancing signal, wherein the at least one drive unit movesthe at least one joint in such a manner that vibrations of the retainingdevice can be balanced out.
 3. The retaining device according to claim1, wherein the lock includes at least one stop surface and at least onecounter-stop surface, configured to interact in order to hold the atleast one joint in the locking position.
 4. The retaining deviceaccording to claim 3, wherein: the lock includes a brake with a movablepart which is coupled with the at least one driven part of the at leastone joint, and the at least one stop surface of the lock is arranged onthe movable part of the brake and the at least one counter-stop surfaceis arranged on the at least one driven part of the at least one joint.5. The retaining device according to claim 4, wherein the brake is anelectromagnetic brake.
 6. The retaining device according to claim 3,wherein the lock includes a stop on which the at least one stop surfaceis formed and which can engage with a recess having at least twocounter-stop surfaces for locking movement of the at least one joint intwo opposite directions of motion.
 7. The retaining device according toclaim 6, wherein the stop is configured to be movable back and forthbetween a first position, in which it locks the movement of the at leastone joint, and a second position, in which it permits the movement ofthe at least one joint.
 8. The retaining device according to claim 6,wherein the stop is a stop pin.
 9. The retaining device according toclaim 3, wherein a clearance is provided between the at least one stopsurface and the at least one counter-stop surface of the lock in adirection of motion of the at least one joint.
 10. The retaining deviceaccording to claim 3, wherein at least one elastic intermediate elementis provided between the at least one stop surface and the at least onecounter-stop surface of the lock in a direction of motion of the atleast one joint.
 11. The retaining device according to claim 1, furthercomprising: a monitoring appliance configured to monitor whether the atleast one joint is being moved within the predetermined range ofmovement and to transmit feedback concerning the movement of the atleast one joint to the securing mechanism.
 12. The retaining deviceaccording to claim 11, wherein the securing mechanism is configured topermit an activation of the lock on the basis of the feedback of themonitoring appliance.
 13. The retaining device according to claim 11,wherein the monitoring appliance includes at least one sensor formonitoring the movement of the at least one joint.
 14. A method foroperating a securing mechanism of a retaining device for an instrument,the method comprising: providing the retaining device including at leastone joint having at least two parts which are moveable relative to oneanother, and at least one drive unit associated with the at least onejoint, the at least one drive unit adapted to move the at least onejoint by driving at least one of the parts of the at least one joint,and the securing mechanism including a lock associated with the at leastone joint and a release unit adapted to be selectively activated,storing, if the release unit is not activated, a locking position andmonitoring a movement of the at least one joint to detect whether the atleast one joint moves, starting from the locking position, within apredetermined range of movement; and activating the lock, if the atleast one joint moves beyond the predetermined range of movement.